Characteristics and Intermediates of Short-Term C14O2 Incorporation During Ribose Oxidation by Hydrogenomonas facilis1

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McFadden, B. A. (Washington State University, Pullman), and H. R. Homann. Characteristics and intermediates of short-term C14O2 incorporation during ribose oxidation by Hydrogenomonas facilis. J. Bacteriol. 89:839–847. 1965.—Ribose-grown cells of Hydrogenomonas facilis, which had been suspended in growth medium and were oxidizing ribose, were exposed to HC14O3− of high specific activity. The uptake was proportional to cell mass. Short-term uptake (less than 2 min) was completely inhibited by 10−3m 2,4-dinitrophenol (DNP) or by <4 × 10−6mm-chlorocarbonyl cyanide phenylhydrazone, and to the extent of 42% by 5 × 10−5m DNP. The following observations were made in kinetic studies (8, 16, 35, 67, 96, and 181 sec) of fixation in the presence of ribose. Glutamate was extensively labeled in periods up to 3 min. It was one of the major early products, containing 30% of the label at 8 sec. The sugar phosphate fraction was not detectably labeled at 8 or 16 sec, but its C14-content increased rapidly to 27% at 35 sec and then slowly decreased. Label in phosphoglycerate, phosphoenolpyruvate, and alanine did not appear until 35 sec, and did not exceed about 7, 2, and 3%, respectively, of the total extracted radioactivity. Adenosine triphosphate and adenosine diphosphate were heavily labeled after fixation in a pilot study for 125 sec. Although considerable radioactivity incorporated during the pilot study was intractable by the extraction procedure employed, virtually no C14 was found in the residue in poly-β-hydroxybutyric acid. A large number of amino acids and organic acids and some organic phosphates were not detectably labeled in any of the experiments. Omission of ribose greatly diminished incorporation, particularly into glutamate.

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